I found it,
function changeDS()
{
var Value;
Value = $('#dt').datetimebox('getValue');
if (!$('#dt').prop('disabled')){
$('#dt').datetimebox({disabled:true,required:false });
}
else{
$('#dt').datetimebox({disabled:false,required:true});
}
$('#dt').datetimebox('setValue',Value);
}
One question: Why the value is lost when set it to
disabled?